However in color-diluted horses carrying the Dun gene, the markings are visible, whereas in non-Dun-gene horses—due to a darker background—these markings are invisible. Castle bases her theory on the fact that you can observe primitive markings in foals that disappear as the animal ages. In general, the color of a horse darkens with maturity, and it is possible that primitive markings remain present. In support of this hypothesis is the presence of such markings on adult horses that are not dun. Such horses are called false duns (see p. 78). The specific mutation of the Dun gene responsible is abbreviated “nd1” (non-dun1). There is a DNA test for the Dun gene. The hierarchy is Dn+ > nd1 > nd2.
Table 4.
| Primary Color | Dn+ |
|---|---|
| Bay | Bay Dun |
| Black | Grullo |
| Seal Brown | Brown Dun |
| Chestnut | Red Dun |
| Buckskin | Dunskin |
| Palomino | Dunalino |
COLORS DETERMINED BY THE SILVER GENE
The colors of this group (Z) were defined rather recently, at the beginning of the twenty-first century. Understanding the true distribution of these colors is difficult because they are rare, although apparently this dilution is present in quite a few different breeds. Color identification in doubtful cases should be guided in part by whether or not a color has shown to be present in a specific breed. Therefore, I feel it necessary to provide a list of breeds in which the Silver gene occurs at the beginning of our discussion. The list includes the: Rocky Mountain Horse, Kentucky Mountain Saddle Horse, Quarter Horse, American Miniature Horse, Morgan, Appaloosa, Missouri Foxtrotter, Virginia Highlander, Paint Horse, Tennessee Walker, Mustang (particularly those found in Oregon, Nevada, and California), Icelandic Horse, Northlands Pony, Australian Pony, Connemara Pony, Shetland Pony, Swedish Warmblood, Finnish Warmblood, Dutch Warmblood, Gypsy Horse, Welsh Pony, Ardennes, Soviet Heavy Draft, and the Byelorussian Harness Horse. It has been determined by DNA analysis that carriers of the Silver gene were also found in the Haflinger breed, but there isn’t a visible color effect because this breed occurs only in the red (chestnut) color. Remember that Silver Dilute horses and dark flaxen chestnuts can look similar.
Silver color displays the following characteristics:
Many silver horses show a characteristic marble pattern on the legs called webbing. This has a “rusty” appearance or looks like whitish, irregular, elongated streaks with sharp boundaries (Photos 45–47).
Ashy or black hair in the mane and tail are found frequently (Photo 48). Silver horses can have yellowish guard hair of a dim, rather dirty shade, but not red or reddish, which would be typical for flaxen chestnuts.
Striped hooves are found in some silver horses, but they are not always present (see Photo 46). They differ from the striped hooves of appaloosa-spotted horses (see p. 55), because the stripes in silver horses are not black, but dark gray, and do not have sharp borders. Often their stripes are wedge-shaped. Striped hooves can be observed in foals, although in the process of the horse maturing, they may disappear.
Pronounced seasonal dapples are observed in some silver horses (silver dapple—see p. 28), appearing in summer and vanishing in winter (Photo 49).
Light eyelashes (white or yellowish), while not present on all silver horses, are a reliable characteristic seen on most (Photo 50).
Silver Bay and Silver Seal Brown
Silver bay is often confused with flaxen chestnut (see p. 39)—for example, in the United States these colors have been recognized as separate entities only since 2002. The silver bay horse has a red or brown color to the trunk and a lighter mane and tail—from dark ashy with separate whitish and yellow locks of hair, to almost completely white (Photo 51). Sometimes the same horse can have a dark and smoky tail paired with an almost white mane, or vice versa. The skin and hooves are pigmented.
The main difference between silver bay and flaxen chestnut are the dark legs, resembling the legs of an ordinary bay horse. In flaxen chestnut animals, the lower part of the legs has a red or whitish color. In the silver bay, the color of the lower part of the legs fluctuates from light to dark brown—to sometimes black. In addition, the ears often have black rims.
A horse with the weakest manifestation of the Silver gene does not differ from an average bay, unless the guard hair is mixed with a considerable amount of light hair, making the mane and tail look ashy. The lower part of the legs is almost undiluted, sometimes showing mild leg webbing. This color may also resemble “Wild” bay or dun, but from the first it can again be distinguished by light guard hair, and from the second by a saturated red color of the trunk and lack of primitive markings. When the body hair of this horse is in poor condition, the color can also be confused with red or brown.
Sometimes you may see a horse with brown body hair and black legs, while the mane and tail are diluted, matching the brown body color. However, the most characteristic and recognizable variety of silver bay has a reddish body, a mane and tail that are nearly white or light ashy, and light brown lower legs because of the presence of leg webbing. Separate ashy or black locks remain in the guard hair.
A silver bay foal has light lower legs, similar in appearance to ordinary bay foals, and becomes darker after shedding his baby coat. Silver bay commonly occurs in the Rocky Mountain Horse.
Silver seal brown is very rare (Photos 52–54). It is recognizable by the dark brown, almost black color of the body, sometimes with a bluish tint to it, with characteristic red “burn marks” around eyes, muzzle, near the elbows, on the stomach, and the groin. The guard hair is diluted from dirty red to a whitish color.
Silver Black and Silver Dapple
There aren’t well-established English terms designated to represent colors determined by the Silver gene on a black base. It is challenging to divide Silvery black color depending on the degree of dilution, because there are diverse phenotypes depending on the degree of Silver expression. Silver black is often a sepia color, usually combined with dapples (Photos 55–59). The guard hair can be from dark brown to light gray or white. Dark silver black horses have a black or dark chocolate colored body, and the mane and tail can have a dark yellow color due to the presence
